Out for the Saturday afternoon ride when I notice that my RD shifter is giving some resistance when I shift; it feels like the cable is binding somewhere. Re-tuning the RD after the ride and visually inspecting the cable, I don't see anything wrong but the shifting is getting worse. Pulling the hood away from the shifter reveals frayed cable coming out of the back of it (sorry no camera). After some frustration I manage to extract the damaged cable from the shifter (the ratchet needs to be zeroed to get the cable out), but I can't figure out how this happened. The cable is three years old, so there's that, but I'm surprised that the cable failed where it did. I can't take the shifter apart or I void the warranty, but I was curious: has anyone else experienced this? Did you find the cause of fraying?

Thanks!